(a) Field of the Invention
The present invention relates to a method for improving a tracking speed of a satellite antenna, and more particularly, to a method in which an external light sensor and a steering angle sensor is used to improve a tracking speed of a satellite antenna.
(b) Description of the Related Art
An increasing number of vehicles are equipped with a satellite signal reception signal. When such a satellite antenna is provided on a vehicle, one of the most important factors to ensure optimal reception is the positioning of the antenna. That is, a central processing unit of an antenna unit monitors a position of the vehicle and of the antenna through a vehicle position sensor and an antenna position sensor. respectively, then performs control to drive a motor that varies the position of the antenna such the antenna is maintained in an optimal reception position.
Accordingly, when driving under normal conditions, a reception signal level is optimized by continuously varying the position of the antenna, that is, by performing a tracking operation that ensures the best possible reception signal. However, when driving under special conditions such as through a tunnel, since a position of the antenna for obtaining an optimal reception signal is not stored in the antenna unit. the tracking operation must again be performed when the vehicle exits the tunnel (i.e., returns to a normal driving condition). Accordingly, the quality of the reception signal deteriorates until the optimal signal level is again obtained.
In the case where a gyro sensor is used, the satellite antenna is moved leftward and rightward after the direction at which the vehicle is traveling is determined. However, if the vehicle is traveling on a slanted road surface, it is determined that the traveling direction of the vehicle is that of the slant. As a result, an optimal reception position is not obtained. Further, in the case where a controller is positioned in-line, the reception performance is deteriorated.
The present invention has been made in an effort to solve the above problems.
It is an object of the present invention to provide a tracking method for a satellite antenna in which tracking is quickly performed, even in the case where satellite signal reception is not continuous.
To achieve the above object, the present invention provides a method for improving a tracking speed of a satellite antenna. The method comprises the steps of receiving image signals and external light signals of a vehicle; determining if a value of the image signals is greater than a predetermined image signal value; re-positioning a satellite antenna if the value of the image signals is less than the predetermined image signal value such that the value of the image signals is increased; maintaining a present position of the satellite antenna if the value of the image signals is greater than the predetermined image signal value; determining if an absolute value of a previous external light signal value subtracted from a value of the present external light signals is less than a predetermined external light signal value, or if a tail light is illuminated, or if an automatic illumination system is operating; determining that the vehicle is travelling through a tunnel or a similarly obstructed location if any of the three conditions of the above step are met, and maintaining a position value of the antenna corresponding to that used directly before one of the three conditions of the above step was satisfied (i.e. a pre-tunnel position value); determining whether the absolute value of the previous external light signal value subtracted from the value of the present external light signals is greater than the predetermined external light signal value; continuously maintaining the pre-tunnel position value if the absolute value of the previous external light signal value subtracted from the value of the present external light signals is less than the predetermined external light signal value; and controlling the antenna as needed if the absolute value of the previous external light signal value subtracted from the value of the present external light signals is greater than the predetermined external light signal value.
According to a feature of the present invention, it is determined that the vehicle is travelling through a tunnel or a similarly obstructed location by using the fact that an average light value during daylight hours is larger than a light value when the vehicle is in a tunnel, and an average light value at night is smaller than the light value when driving in a tunnel.
In another aspect, the method of tracking a satellite antenna in a vehicle equipped with a steering angle sensor comprises the steps of establishing a steering angle sensor value to a predetermined angle value from a present vehicle position; detecting an image signal according to the predetermined angle value; comparing an image signal state with a predetermined standard value; fixing a satellite antenna position to a position when detecting the image signal in the case where the image signal state satisfies the predetermined standard value; and re-positioning the satellite antenna by a predetermined angle in the case where the image signal state does not satisfy the predetermined standard value.
According to a feature of the present invention, the steering angle sensor is used both to determine the direction at which the vehicle is travelling and for tracking the satellite antenna position.